The Premier League champions flew to Thailand to begin their pre-season tour without the Serbian defender, who is suffering from sciatica - pain that comes from nerves in the back.

But although Vidic has suffered from injuries over the last two seasons, when he has only started 24 league games, they are confident he will not be sidelined for long.

"It's nothing serious," a club spokesperson told the club's official website. "Nemanja has a touch of sciatica and may still join the tour at a later date.

"In the meantime, he'll continue his pre-season preparations in Manchester at the Aon Training Complex."

After going to Thailand, United visit Japan, Hong Kong and Australia, perhaps with Vidic, and his fellow centre-back Rio Ferdinand said that the battle to earn a place in new manager David Moyes' first competitive side has already begun.

He told MUTV: "I think it's natural that everybody here is trying to impress on this tour. When you get a new manager you want to show him that you should be in the starting XI for that first day of the new season and that process has started already."